Acne vulgaris, I: pathogenesis and diagnosis.

Acne vulgaris is a chronic inflammatory disease of the pilosebaceous units. It is a pleomorphic disorder with multifactorial pathogenesis. The many expressions of acne rarely present a diagnostic challenge, but correct classification of acne is crucial in choosing the appropriate therapies. Although previous research has provided a better understanding of the pathogenic factors, there is still a great deal to be learned.